How to calculate a tip in your head
The fastest mental shortcut in the US is the "move and double" trick. Take the bill, move the decimal one place to the left (that's 10%), then double it for 20%.
Example: a $54.80 check. Ten percent is $5.48. Double it — about $11. Add it to the bill and you're at roughly $66 total. For 15%, take that 10% number and add half of it again. For 18%, take 20% and shave a little off.
Need every method — 15%, 18%, 25%, the "double the tax" trick and tipping on a $114 bill — worked through step by step? Read how to calculate a tip.
This calculator does the same arithmetic, but it also handles the awkward part: the split. Three people, uneven orders, one person ordered drinks — that's where mental math falls apart and a calculator earns its keep.
Tip on pre-tax or post-tax?
Old-school etiquette says tip on the pre-tax subtotal. In practice, the post-tax number is the one printed at the bottom of the bill, and most people just tip on that. Both are accepted.
The math difference is small. On a $50 meal with 8% sales tax, tipping 20% on pre-tax gives the server $10. Tipping 20% on the post-tax $54 total gives them $10.80 — eighty cents. Nobody at the table will judge you either way.
If you want to be precise, enter the pre-tax subtotal above. If you'd rather just tip on the bottom-line number, enter that. The calculator doesn't care which one you use.